A large quantity of new materials with different functions is used in modern science and technology. These functional materials must be of high-purity, or a certain impurities are intentionally doped into the high-purity materials to form doped materials. However, it is difficult to meet these requirements through many traditional preparation methods, such as high-temperature smelting and precipitation, crystallization in aqueous solutions, and the like. Therefore, it cannot be ensured to obtain high-purity products.
Chemical vapor deposition (CVD) is a process that reactive materials are subjected to chemical reaction under a gaseous condition so as to generate a solid substance deposited on the surface of a heated solid matrix, so that a solid material is obtained. The process essentially belongs to a gaseous mass transfer process in the atomic domain.
As a new technology, CVD has been developed in recent decades for preparation of materials. The CVD method has been widely used for extracting materials, developing new crystals, and depositing various monocrystalline, polycrystalline or vitreous film materials. These materials may be oxides, sulfides, nitrides and carbides, or binary or polynary element compounds in III-V, II-IV and IV-VI families, and the physical functions of the materials can be accurately controlled through a vapor doping deposition process.
In contrast, physical vapor deposition (PVD) is a process that the surface of a material source, namely a solid or liquid, is gasified into gaseous atoms or molecules or partially ionized into ions under vacuum by adopting a physical method, and a film with a certain special function is deposited on the surface of a matrix through a low-pressure gas (or plasma) process. Main methods of PVD include vacuum evaporation, sputter coating, arc plasma plating, ion coating, molecular beam epitaxy and the like. At present, the PVD technology may not only be used for depositing metal films and alloy films, but also may be used for depositing compounds, ceramics, semiconductors, polymer films and the like.
A vapor deposition apparatus generally includes a reaction chamber, a gas supply system and a heating system. The reaction chamber includes a support for supporting a substrate to be treated, such as lift pins and the like, and the heating system includes a heating plate for example, on which a heating resistance wire is arranged.
A display panel treated by the vapor deposition process often suffers a phenomenon of mura due to process uniformity. This phenomenon may be caused by a structural design which has to be complied with on machine hardware in the manufacturing process, or by inherent compatibility restriction between raw materials and the technology. Consequently, the phenomenon of mura with a fixed shape and a fixed range of size will be generated at a specific position of a large glass plate.
Upon investigation, the inventors found the source for the technical problem.
FIG. 1 schematically shows a heating plate 10 in a vapor deposition apparatus for treating a glass substrate in the prior art. With reference to FIG. 1, a heating resistance wire 3 is generally arranged on the heating plate 10 in the vapor deposition apparatus for treating the glass substrate, and lift pins 2 are placed exactly corresponding to the position of the glass substrate in a display area.
FIG. 2 shows a schematic diagram of a vapor deposition process for a glass substrate 1 of a display. Correspondingly, in the vapor deposition process for the glass substrate 1, the glass substrate 1 may be heated in a non-uniform manner in view of the presence of the lift pins 2 and the resistance wire 3. Generally speaking, the temperature at a position corresponding to the resistance wire 3 is relatively high, whereas the temperatures at the positions corresponding to the lift pins 2 are relatively low. Therefore, the process quality and optical property of the glass substrate will be negatively affected. As a rule, the glass substrate treated through the vapor deposition process has a relatively low transmittance at the positions corresponding to the lift pins 2 or the resistance wire 3, so that the display panel finally obtained suffers from the phenomenon of mura. This significantly reduces the performance and value of the display panel.